1. Field of the Invention
The present invention relates to an IC chip package and, more specifically, to a small size IC chip package, which greatly reduces the dimensions of the whole package.
2. Description of the Related Art
Because regular IC chips are fragile, they must be well packaged and protected against external force. After packaging of an IC chip, the IC chip can be effectively electrically connected to an external circuit board. Following fast and free development of high-tech, IC chip packages are made lighter, thinner, shorter, and smaller. FIG. 1 illustrates an IC chip package 1 according to the prior art. According to this design, the IC chip package 1 comprises a substrate 3, the substrate 3 having a passage 3a through the top and bottom sides thereof, a chip 2 fixedly mounted on the topside of the substrate 3, the chip 2 having a plurality of bonding pads 2a disposed at one end of the passage 3a, a plurality of bonding wires 4 extended through the passage 3a, the bonding wires 4 each having one end respectively connected to the bonding pads 2a of the chip 2 and the other end connected to bonding pads 3b on the substrate 3, two protective covers 5, 5′ respectively covered on the chip 2 and the bonding pads 3b and bonding wires 4 of the substrate 3, a solder mask 7 covered over the circuits 6 of the substrate 3, and a plurality of solder balls 8 respectively electrically connected to the conductive circuit pattern 6 outside the solder mask 7 and adapted for connecting the conductive circuit pattern 6 to tin solder paste 9a pre-applied on an external circuit board 9.
According to the aforesaid package 1, the bottom side of the substrate 3 must leave sufficient space for receiving bonding wires so that the bonding wires 4 can be extended through the passage 3a and connected between the bonding pads 2a at the chip 2 and the bonding pads 3b at the substrate 3. When the protective cover 5′ covered on the whole area of the bonding pads 3b on the substrate 3b and the bonding wires 4, the vertical height H of the protective cover 5′ between the bottom side of the protective cover 5′ and the substrate 3 is tall. Therefore, a relatively higher interface must be used for enabling the substrate 3 to be electrically connected to the external circuit board 9, i.e., the solder balls 6 must be greater than the vertical height H of the protective cover 5′ for soldering to the solder paste 9a at the external circuit board 9. According to this design, the vertical height of the solder balls 6 is about 0.5 mm. The use of the big solder balls 6 greatly increases the dimensions of the IC chip package 1.